The ARQ (Automatic Request for Repetition) means that a reception side requires a repeat of data with voluntary unit of data quantity (for instance, unit per packet, unit per cell) to transmission side. Three systems of Stop And Wait ARQ (SW-ARQ) system, Go Back N ARQ (GBN-ARQ) system, and Selective Repeat ARQ (SR-ARQ) system are well known as system of the ARQ.
Further, recently, a system of PRIME-ARQ is proposed. The PRIME-ARQ system combines the GBN-ARQ system and the SR-ARQ system. The GBN-ARQ system retransmits all of packets or cells finished transmission, whose temporal order is later than an instructed sequence number (hereinafter referred to as SN). The SR-ARQ system retransmits only the packets or the cells corresponding to the instructed SN.
In the PRIME-ARQ system, retransmission is performed in accordance with following procedure. A reception side finds SN corresponding to packets or cells that are not received. The reception side returns prescribed numbers of the SN corresponding to packets or cells that are not received by way of ARQ control information to a transmission side. The transmission side retransmits the packets or the cells corresponding to the SN instructed on the basis of the ARQ control information received. The transmission side retransmits about all of the packets or the cells finished transmission that are followed on the heels of the latest SN about temporal order from among the SN undergoing repeat instruction.
Hereinafter, there will be described about the PRIME-ARQ system while employing FIG. 1 as well as FIG. 2. FIG. 1 is a block diagram indicating rough configuration of a transmission-reception apparatus for performing error control of the PRIME-ARQ system. FIG. 2 is an operational diagram indicating one example of sequence of the PRIME-ARQ system. Moreover, in this stage, the ARQ is performed with unit of the packet.
Moreover, in this stage, unidirectional data transmission is supposed, consequently, configuration of the transmission-reception apparatus is indicated while being separated into a transmission side and a reception side. Furthermore, in view of characteristic of the present invention, the present description indicates only configuration concerning retransmission control.
In FIG. 1, the transmission side includes a transmission buffer 1 for giving the SN to transmission data packet to store therein, a modulator 2 for performing modulation processing while adding CRC (cyclic redundancy check) to the transmission data packet, a D/A converter 3 for performing D/A conversion processing to a transmission signal after modulation processing, a transmission RF section 4 for transmitting a transmission signal after D/A conversion from an antenna (not illustrated), a reception RF section 5 for receiving radio signals from an antenna (not illustrated), an A/D converter 6 for performing A/D conversion of reception signal, a demodulation processor 7 for performing demodulation processing as well as CRC check to reception signal after A/D conversion to extract ARQ control information, and a retransmission controller 8 for instructing to retransmit the SN undergoing retransmission requirement to transmission buffer 1 on the basis of the ARQ control information from among the reception signals.
On the other hand, a reception station includes a reception RF section 9 for receiving radio signals from an antenna (not illustrated), an A/D converter 10 for performing A/D conversion of the reception signal, a demodulation processor 11 for performing demodulation processing as well as CRC check to the reception signal after A/D conversion, a SN judgement section 12 for performing check of the SN given to the data packet to the reception signal after demodulation processing to perform judgement of SN omission as well as removal of SN information, a reception buffer 13 for storing therein the data packet of the reception signal after removal of the SN information, a retransmission control information generator 14 for generating ARQ control information from judgement result in the SN judgement section 12, a modulator 15 for performing modulation processing while adding the CRC to the ARQ control information generated, a D/A converter 16 for performing D/A conversion of the transmission signal after modulation processing, and a transmission RF section 17 for transmitting the transmission signal after D/A conversion from an antenna (not illustrated).
In the first place, there is described operation of the transmission side. Inputted transmission packet to which the SN is added is stored in the transmission buffer 1. The stored transmission packet is outputted on the basis of repeat SN instructed from the retransmission controller 8 by the transmission buffer 1. The data packet outputted from the transmission buffer 1 is transmitted from an antenna (not illustrated) through the modulator 2, the D/A converter 3, and the transmission RF section 4.
The signal received by the reception RF section 5 is inputted to the retransmission controller 8 through the A/D converter 6 and the demodulation processor 7, and the SN undergoing retransmission requirement is instructed to the transmission buffer 1.
Next, there is described operation of the reception side. The signal received by the reception RF section 9 is inputted to the SN judgement section through the A/D converter 10 and the demodulation processor 11. Then, the signal is judged about omission of the data packet on the basis of the SN which is added to respective data packets of the reception signals by the SN judgement section 12. The SN with omission is outputted to the retransmission control information generator 14 as judgement result.
The omission of the data packet among the reception signal is converted into the ARQ control information by the retransmission control information generator 14 to be outputted. The generated ARQ control information is transmitted from an antenna (not illustrated) by the transmission RF section 17 through the modulator 15, and the D/A converter 16. Furthermore, the data packet which is judged as receivable by the SN judgement section 12 is inputted to the reception buffer 13 to be stored therein while being removed the SN from the data packet.
Subsequently, there is described one example of sequence in the PRIME-ARQ system while employing FIG. 2.
In FIG. 2, it is indicated that in a first frame transmission from the transmission side, packets #1 to #9 (SN=1 to 9) are transmitted, while in the reception side, reception of the SN=2, 4, 5, 8 is failure.
Here, when the number of the ARQ control information determined before hand is taken to be three (3), the reception side performs the retransmission requirement about three packets of SN=2, 4, 5 while employing the ARQ control signal. The transmission side receives the ARQ control signal, then, performing retransmission about the packet finished transmission whose SN is equal to 2, 4, 5 as well as after SN corresponding to 6. The reception side neglects the packet finished reception.
Thus, in the PRIME-ARQ system, since it is capable of performing many retransmission requirements with small data quantity, transmission efficiency improves in comparison with the conventional three systems.
However, in the error control of the conventional PRIME-ARQ system, there is the problem that when there occurs burst error more than the number of SN which is capable of being represented by the retransmission control information, transmission efficiency deteriorates. Furthermore, when the system increases quantity of retransmission control information for improvement of error rate, there occurs the problem that the transmission efficiency deteriorates.